Current transgenic methods include viral techniques, lipofection, microparticle bombardment, and paddle electroporation (Leber et. al 1996; Methods Cell Biol. 51: 161–83; Muramatsu et. al 1997; Bioc Biophys Res Comm. 23: 376–80). Electroporation is a versatile and popular method of transfecting cells by briefly subjecting them to an electric field, which forms pores in the lipid bilayer, and allows entry of compounds into the cytoplasm (Lurquin 1997; Mol Biotechnol. 7 (1): 5–35). Electroporation overcomes the disadvantages of viral techniques, such as small insert size and biohazard concerns (Leber et. al 1996; Methods Cell Biol. 51: 161–83). Additionally, electroporation has been shown to be more efficient than other methods of in ovo transfection, such as lipofection or microparticle bombardment (Muramatsu et. al 1997; Bioc Biophys Res Comm. 23: 376–80). However, previous electroporation efforts have had a number of limitations, including the inability to effectively target the electroporation, lack of reproducibility of results, and exposure of non-targeted cells to potentially damaging current. Specifically, the electroporation apparatuses of the prior art are generally paddle-like pairs of electrodes, having inherent limitations as to how small a target area would be electroporated and lacking integral means for introducing the foreign matter (commonly DNA) into the cells. Instead, the prior art teaches separate injection of the foreign matter into a localised target area, and electroporation of a larger region including and extending beyond the target area. Accordingly, the prior art teaches unnecessary electroporation of (and thereby potential attendant injury to) cells outside the target area.
Moreover, methods of electroporation in the prior art have proved inefficient and unreliable in localising to any degree the transfection events, and cannot target a specific region of an organ or tissue. Truly localised electroporation could neither be accomplished with prior methods, nor was it contemplated. Prior art methods of in ovo electroporation have involved subjecting the entire embryo to potentially damaging current and the effects have been difficult to reproduce. Although prior art in vivo efforts have included attempts to target on particular organs or tissues, these efforts have involved the injection of a DNA-containing solution into an organ or into the blood stream of an organism and the use of paddle-like pairs of electrodes for the application of the electric field. Cells and tissues subjected to these prior art methods would be not be uniformly electroporated, and as a result only random transfection events would occur within the selected areas. Introduction of foreign compounds other than genetic material by electroporation has likewise suffered from a high degree of unpredictability, due to the inefficiency and unreliability of prior art methods of electroporation.